New Argon Reference Gas

We have developed a new reference gas for standardizing 40Ar/39Ar measurements made with a multicollector array.  This gas was prepared at the USGS in collaboration with Andy Calvert (USGS) and Dawn Kellet (Canadian Geologic Survey).  The gas mixture was optimized from that previously described in Coble et al. (2011).  The mixture was generated by adding ³⁹Ar to previously created ⁴⁰Ar:³⁶Ar = 30 (UO46) and ³⁸Ar pipette systems (UO39) (Miiler, 2006).  Two separate aliquots of the same reference gas are currently being used to standard both multicollection and IC monocollection measurements on the Stanford and USGS (Menlo Park) USGS instruments.  At Stanford, the reference gas has been in use since June, 2015. The relative standard error of the mean calculated from the current calibration (42315) was 0.11 ‰ (2 sigma; MSWD = 3.3) for 274 40Ar/39Ar multicollection measurements detrended for multiplier aging.

• M. A. Coble, M. Grove, A.T. Calvert, 2011, Calibration of Nu-Instruments Noblesse multicollector mass spectrometers for argon isotopic measurements using a newly developed reference gas. CHEMICAL GEOLOGY, 2011; 290 (1-2): 75-87
• A.P. Miiller, 2006, Development of Argon Isotope Reference Standards for the U.S. Geological Survey, J. Res. Natl. Inst. Stand. Technol. 111, 335-360.